1. Field of the Invention
The invention relates to the field of ski-supported vehicles. More particularly, the invention relates to snowmobiles equipped with wheels that will allow the snowmobile to travel readily over surfaces not covered with snow or ice.
2. Description of the Prior Art
Snowmobiles are vehicles that are constructed to travel across snow and ice. As is generally known, the snowmobile is driven by an endless drive track arranged at the rear end of the underside of the snowmobile. The front end of the snowmobile is supported and rides along two skis, which glide across the surface of the snow or ice. The skis typically have a carbide runner that runs along a portion of the bottom surface of the ski, to help keep the snowmobile traveling along a smooth track.
A disadvantage of snowmobiles is that the skis don""t readily glide across gravel, hardtop, or other non-snow surfaces. This makes it difficult, if not impossible, to steer a snowmobile because the skis do not respond properly to the steering operations initiated at the handlebars. Quite often, the snowmobile needs to be dragged or pushed in driveways and across roadways, etc. Furthermore, when a snowmobile is driven or dragged across a non-snow surface, the carbide runners on the skis are subject to excessive wear and must be replaced more frequently, depending on how often a snowmobile travels across a non-snow surface. This inability to steer snowmobiles on surfaces other than snow and ice makes it difficult for people to maneuver their snowmobiles across roadways, driveways, onto ferries, etc.
In recent years, the sport of snowmobiling has changed evolved from one of traveling relatively short distances over trails close to home to one of weekend-long or longer cross-country trips. Previously, for example, a snowmobile operator would fill the gasoline tank of the snowmobile in his or her backyard, transport the snowmobile to a trail site or depart directly from the backyard for an afternoon or day of travel over snowmobile club trails, and then return home. Nowadays, people are traveling great distances across country on snowmobiles that involve two-or three-day tours or even such mammoth tours as from Alaska to Maine.
This development of the sport of snowmobiling into extended trips means that snowmobiles must now be refilled with gasoline and maintained while they are out traveling across open country. Thus, where in the past the tank on the snowmobile was filled at home or at the point of departure before a daylong excursion, snowmobiles now need to be refilled while out traveling. This means that the snowmobile must be driven to a service station, typically by traveling some distance along a road surface other than snow or ice. Also, now that such lengthy trips are being undertaken with snowmobiles, the presence of snow along the entire route is not guaranteed, and consequently, snowmobiles are being required more and more frequently to travel some distance across surfaces other than snow or ice. Before, when a snowmobile needed to be dragged or pushed only a short distance across a roadway or driveway, or up a ramp onto a ferry, it was possible for a person to do it alone or with the assistance of a traveling companion. Now, however, with the need to travel several miles along a roadway to get to a filling station, the inability to steer a snowmobile has become a major obstacle in the logistics and the enjoyment of the sport.
Efforts to make snowmobiles mobile on gravel or other surfaces have been undertaken over the years. Prior art includes conversion kits to replace the skis with wheels. These conversion kits were intended to replace the skis on a semi-permanent basis, that is, to convert a snowmobile into a wheeled vehicle for an extended period of time. Such conversion kits typically require that the ski be removed in order to mount the wheels, or, if the ski does remain attached to the vehicle, a longer kingpin must be used to mount the wheels. Thus, each time the wheels are mounted or removed, the kingpin must be replaced with the longer or shorter one, respectively. Both methods of converting the snowmobile to a wheeled vehicle involve a fair amount of work. Thus, such conversion kits are not generally an acceptable solution to the problem of having to change in relatively quick succession back and forth between a vehicle that rides on skis and one that rides on wheels, as happens when traveling over gravel or hardtop or other surface other than snow or ice to fill the gas tank or to load onto a ferry.
What is needed, therefore, are means for quickly converting a vehicle back and forth between one that glides on skis to one that rolls on wheels. What is further needed are such means that do not impair the steerability of the vehicle. What is yet further needed are such means that are easily implemented, without requiring great physical strength and without requiring the use of tools. What is still yet further needed are such means that are retrofittable on any conventional snowmobile ski.
An object of the present invention is to provide a combination ski-wheel unit that will allow one to convert a ski-supported vehicle quickly and easily to a wheeled vehicle and back to a ski-supported vehicle, without requiring the use of tools. Another object of the present invention is to provide such a unit that will maintain the steerability of the vehicle, whether on skis or on wheels. A further object is to provide such a unit that, once installed, can be easily deployed without requiring great physical strength. Still another object is to provide a wheel kit with deployable wheels that can be retrofitted onto any conventional snowmobile ski.
The objects are achieved by providing a road wheel unit having one or more wheels that is permanently or semi-permanently installed on the ski of a conventional snowmobile so as to provide easily deployable or retractable wheels, as the conditions require. In a retracted position, i.e. the standard snowmobile mode of operation, the wheel is carried alongside the ski, raised above the gliding surface of the ski. In a deployed position, the wheel is lowered, so that the weight of the machine is supported by the wheel. In this deployed position, the wheel unit holds the ski above the rolling surface of the wheel and allows the snowmobile to ride on wheels and the conventional endless track at the rear end. In the deployed mode, the snowmobile remains readily steerable with the handlebars, and the carbide runners on the ski surfaces are not subject to excessive wear. Ideally, the wheel or wheels of the wheel unit are easily detachable from the mounting means, leaving the mounting means permanently installed on the vehicle, without impairing the functionality of the skis. As mentioned above, a wheel unit has one or more wheels. Generally, at least one wheel is mounted on each of the two skis of the snowmobile and, thus, the term xe2x80x9cwheelsxe2x80x9d is generally used hereinafter, although it is understood that, depending on the type of wheel unit, only one wheel may be mounted on a ski.
There are various types of conventional skis. Some have a kingpin assembly for linking the ski to the snowmobile; other skis have built-up sidewalls and/or a saddle-shape protrusion extending from the sidewall that is constructed with sufficient strength and rigidity to support a linking assembly that links the ski to the snowmobile. The scope of the invention includes a wheel unit that is mountable on the kingpin that links the ski to the snowmobile, as well as a wheel unit that is mountable on the side wall or the saddle of the ski, or onto a mounting block that is integrated into the side wall construction of the ski. The wheel unit mountable on the kingpin is hereinafter referred to as the kingpin-mount wheel unit; the unit mountable on the side wall, saddle, or onto a mounting block integrated into the side wall construction is referred to as the side wall-mount wheel unit; and a unit that is mountable on virtually any type of ski, that is, on a kingpin assembly, on a side wall or saddle is referred to as the universal wheel unit.
Each wheel unit includes one or two wheels and a deployment mechanism that allows the wheels to be deployed or retracted. When a pair of wheels is mounted on one ski, i.e., one wheel on each outer side of the ski, the deployment mechanism ideally simultaneously deploys the wheel on both sides of the ski.
The deployment mechanism is ideally a relatively simple mechanical shifting and locking mechanism that allows the operator to easily shift the wheel unit between a deployed wheel position and a retracted wheel position and to securely lock the wheel unit in the respective position. One deployment mechanism that is suitable includes a side rail that is shiftably attached to the wheel unit and a latching mechanism for latching the wheel unit into a first or deployed position and into a second or retracted position. For example, a latch is mounted on the ski or on the wheel unit and the wheel unit locked into position by catching the latch in the first position or in the second position on the rail. The first and second position may be connected by a groove and the latch itself may be a pin that is captured at one end in the groove and is slidably movable into the first position or into the second position, where it is secured against unintentional release.
Another suitable deployment mechanisms for securing the wheel unit has at least two latch bores, depressions, or latch-receiving assemblies that are provided on the ski, either on the side wall or on a rail attached to the ski or attached to the wheel unit. Each of the latch bores, etc. corresponds to a particular position of the wheel unit. Thus, a first position corresponds to a position state and a second position to a retracted position of the wheel unit. A latch that is mounted on the wheel unit is securable in one or the other latch bores. For example, a handle with a spring-loaded button or bar is pivotably attached to the wheel unit. The wheel unit is secured in the deployed or retracted position by pulling on the handle to release the button from the respective latch bore, moving the handle to the desired position and allowing the button or bar to snap into the respective other latch bore.
Generally, the deployment mechanism incorporates a locking mechanism for locking the wheel unit into position, as described above. It is possible, however, to provide a separate locking mechanism in the ski to ensure that the wheel unit is locked into the respective deployed-wheel or retracted-wheel position. In an embodiment in which two wheels are mounted on a ski, a side rail is pivotably mounted each side of the ski and a yoke used to connect to each side rail to gang them together. A latching mechanism is mounted on the floor of the ski. The yoke depends down into the inner contour of the ski and the bottom portion of the yoke latches into the latching mechanism.
It is important that the wheel unit be easily deployable by a person of average strength. To deploy the wheel unit having a deployment mechanism that includes a side rail and latching pin, the operator lifts the ski by the handle that is typically provided at the front end of the ski, grabs hold of the crossbar (if two side rails are ganged with a crossbar) or the latching pin, and slightly lifts and slides the crossbar or the latching pin forward toward the front end of the ski until the it latches in the first or deployed position. This effectively lowers the wheel or wheels and locks the wheel unit into place. The snowmobile is now drivable across gravel and hardtop surfaces without losing its ability to be steered with the handlebars. To retract the wheels, the procedure is reversed. The operator lifts the ski until the weight of the snowmobile is off the wheels, grabs the crossbar or latching pin and slides it toward the rear end of the ski until it latches in the second or retracted position. The wheel or wheels are now secured in a raised or retracted position in which the lowest point of the wheels is above the gliding surface of the ski, allowing the snowmobile to glide fully on the skis.
In some cases, it is desirable or necessary to mount the wheel unit on the side wall or saddle of the ski, rather than on a kingpin. The side wall-mount wheel unit is provided for this purpose. The side wall-mount wheel unit includes a mounting plate that is mountable on the side wall or on the saddle. The wheel-mounting bracket is mounted on a spindle that extends from the mounting plate. As with the kingpin-mount wheel unit, either one wheel or a pair of wheels is mounted on each ski. Again, if a pair of wheels is mounted on the ski, a crossbar or some other means is ideally used to gang or link the two side rails, so that moving the deployment mechanism causes both side rails to move simultaneously, thereby ensuring that the wheels are deployed/retracted simultaneously.
A universal wheel unit according to the invention is provided that is mountable on virtually any conventional ski. The universal wheel unit is mountable on a kingpin mount, on the side wall, or on the saddle of a ski and is particularly well-suited for mounting a single wheel on a ski, rather than a pair of wheels.
It is within the scope of this invention to include an automatically actuatable wheel unit for ski-mounted vehicles. The deployment mechanisms described above involve simple mechanical actuation. Any number of known automated or power-assisted means of actuating a cam mechanism are suitable for deploying and retracting the wheels. In one embodiment, the latching mechanism is spring-biased toward the retracted position, so that, when the snowmobile weight is lifted from the ski, the wheel unit automatically shifts to a xe2x80x9cretractedxe2x80x9d position. Other means for actuating the deployment mechanism according to the invention include such means as a pivot arm or linkage driven by an electric motor, an electro-magnetic means in which magnets are selectively magnetized to draw the deployment mechanism to a deployed or retracted position, or hydraulic or pneumatic means. A small electric motor is mountable within the inner contour of the ski, for example, and then wired to a thumb switch on the handlebar of the snowmobile. The motor drives a shaft that is connected to an arm that is pivotably linked to the side rail or frame. When the shaft extends, the deployment mechanism is pushed to a deployed position, thereby lowering the wheels to an operable level, and when the shaft retracts, it pulls the deployment mechanism to a retracted position, thereby lifting the wheels above the level of the gliding surface of the ski. An indicator, for example, a warning light, connected either to the deployment mechanism or the power-assisted actuating means, may be mounted on the dashboard or on the handlebar to alert the operator when the wheel unit is deployed.
Although it is desirable that snowmobiles be sold already equipped with skis having a wheel unit according to the present invention, a wheel kit is provided for retrofitting a typical ski for any number of the conventional snowmobiles already available. In most cases, the ski itself need not be modified. When retrofitting a ski with a kingpin link to receive the kingpin-mount wheel unit, the original kingpin may need to be replaced with a modified, longer kingpin, to which the kingpin-mount wheel unit is then attached. When retrofitting a ski that does not have a suitable kingpin mounting assembly, or if a side-wall mounting is desired for other reasons, a sidewall-unit mounting plate is either mounted over the double-scag fastening posts or fastened to the side wall or saddle of the ski; the wheel deployment mechanism and wheel assembly are then mounted on the plate. The universal wheel unit is mountable on the modified kingpin, on the side wall, over the double-scag fastening posts, or on the saddle of the ski, depending on the type of ski. Regardless of which type of actuation means is installed, manual, electric, or other, a switch and/or an indicator light is retrofittable on the dash of the snowmobile.
With the wheel unit according to the invention, the wheels are semi-permanently mounted on the ski. Depending on the particular travel conditions, the wheels are deployed, so that the snowmobile becomes a wheeled vehicle, or retracted, so that the wheels are carried along side the ski in a raised position, above the gliding surface of the ski.